it can be over excited

it has two sets of rotor poles

both its rotor and stator are excited

it needs twice the normal exciting current

stabilize rotor motion

suppress rotor oscillations

develop necessary starting torque

both 1) suppress rotor oscillations and 2) develop necessary starting torque

damper winding in its pole faces

magnetic locking between stator and rotor poles

induced e.m.f. in rotor field winding by stator flux

compulsion due to Lenz's law

excitation current and back e.m.f.

field current and power factor

D.C. field current and A.C. armature current

armature current and supply voltage

power factor

torque angle

back e.m.f.

armature current